In a medium bowl, whisk together ½ cup (120 grams) warm water, warm milk, 2 teaspoons (8 grams) sugar, and yeast. Let stand until foamy, 5 to 10 minutes.

In the bowl of a stand mixer fitted with the paddle attachment, beat flour, salt, and remaining 4 teaspoons (16 grams) sugar at low speed until combined. Add yeast mixture, 1 egg (50 grams), and melted butter, and beat at low speed for 2 minutes.

Switch to the dough hook attachment. Beat at low speed until a soft, somewhat sticky dough forms, stopping to scrape sides of bowl, 6 to 8 minutes. (Dough should pass the windowpane test; see Note.) Turn out dough onto a very lightly floured surface, and gently shape into a ball.

Spray a large bowl with cooking spray. Place dough in bowl, turning to grease top. Cover and let rise in a warm, draft-free place (75°F/24°C) until doubled in size, 30 to 45 minutes.

Preheat oven to 375°F (190°C). Line 2 baking sheets with parchment paper.

Punch dough down, and let stand for 10 minutes. Divide dough into 10 portions (about 78 grams each). Using a rolling pin, flatten each portion into a 5-inch circle. Spoon 2 tablespoons (31 grams) Beef Filling into center of each circle. Pinch edges of each circle together around filling, and turn seam side down. Cup dough ball with your fingertips touching the surface; swirl dough on surface twice to shape into a roll and place 2 ½ to 3 inches apart on prepared pans.

In a small bowl, lightly whisk remaining 1 egg (50 grams). Brush each roll with egg.

Bake until deep golden brown, 18 to 20 minutes.